1. Field of the Invention
The invention relates to an electrical rotating data transmission device, especially for use in computer tomographs. In this, a transmission of digital image data obtained by an X-ray detector is effected without contact between a rotatable gantry and a stationary part of a computer tomograph. Furthermore, data also may be transmitted in the opposite direction to control the rotatable gantry.
2. Description of the Prior Art
According to known prior art, image data are transmitted via a broadband data path that is preferably non-contacting, whilst relatively slow control and monitor data are transmitted via separate slip-ring paths having a smaller bandwidth. For this, two independent transmission technologies are employed with a large attendant technical outlay. Further development of this prior art is disclosed in U.S. Pat. No. 6,292,919. In this, a data transmission of video data is effected by means of a TAXI chip set. This chip set is described in the data sheet “TAXIchip Integrated Circuits, Transparent Asynchronous Transmitter/Receiver Interface Am7968/Am7969” by Advanced Micro Devices (AMD), 1994. The chip set consists of a transmitter having a parallel-serial converter for converting parallel data to a serial data stream, and a receiver for converting the serial data stream to parallel data. An encoding of the data for transfer is effected by means of a 4B/5B code. With this 4B/5B encoding, an additional redundancy is introduced into the data stream. Thus, 8 Bit data words are converted to 10 Bit data words for transmission. With this, the two additional bits are not contained in the data stream at fixed given positions, but are used for forming additional codes which may be transmitted in addition to the codes needed for representing the data. Some of these additional codes are designated as command codes and may be triggered by separate control inputs on the TAXI chip set. A receiver is equipped to signal a receipt of such codes. Other codes are used for error recognition and are recognized as being inadmissible.
Now, according to the cited prior art, in some computer tomographs command codes adapted to be triggered by separate control inputs are utilized for signaling additional states (view start commands). By intelligent evaluation of the TAXI-chipset in the receiver, the control codes are recognized as such, and the presence of such a control code is signaled as a view start command to units connected to the receiver. At the same time, a data clock as is usually issued upon receipt of data is not issued, so that an erroneous evaluation of control codes as being data, made by units connected to the receiver, is not possible. With this prior art it is disadvantageous that the proposed signaling procedure can be effected exclusively by means of TAXI chips from the semiconductor manufacturer AMD. Parallel/serial converters as usually employed for communication do not have available any control inputs for emitting additional signaling codes.